全文获取类型
收费全文 | 23464篇 |
免费 | 1262篇 |
国内免费 | 231篇 |
专业分类
化学 | 16948篇 |
晶体学 | 185篇 |
力学 | 503篇 |
综合类 | 8篇 |
数学 | 3162篇 |
物理学 | 4151篇 |
出版年
2023年 | 206篇 |
2022年 | 167篇 |
2021年 | 290篇 |
2020年 | 424篇 |
2019年 | 432篇 |
2018年 | 418篇 |
2017年 | 411篇 |
2016年 | 844篇 |
2015年 | 782篇 |
2014年 | 814篇 |
2013年 | 1620篇 |
2012年 | 1737篇 |
2011年 | 1926篇 |
2010年 | 1007篇 |
2009年 | 832篇 |
2008年 | 1645篇 |
2007年 | 1613篇 |
2006年 | 1392篇 |
2005年 | 1315篇 |
2004年 | 1048篇 |
2003年 | 922篇 |
2002年 | 814篇 |
2001年 | 425篇 |
2000年 | 401篇 |
1999年 | 261篇 |
1998年 | 203篇 |
1997年 | 196篇 |
1996年 | 256篇 |
1995年 | 169篇 |
1994年 | 163篇 |
1993年 | 203篇 |
1992年 | 157篇 |
1991年 | 106篇 |
1990年 | 93篇 |
1989年 | 95篇 |
1988年 | 79篇 |
1987年 | 71篇 |
1986年 | 102篇 |
1985年 | 152篇 |
1984年 | 134篇 |
1983年 | 77篇 |
1982年 | 107篇 |
1981年 | 95篇 |
1980年 | 94篇 |
1979年 | 66篇 |
1978年 | 75篇 |
1977年 | 58篇 |
1976年 | 62篇 |
1975年 | 45篇 |
1974年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Algebraic Formulation of Quantum Decoherence 总被引:1,自引:0,他引:1
An algebraic formalism for quantum decoherence in systems with continuous evolution spectrum is introduced. A certain subalgebra, dense in the characteristic algebra of the system, is defined in such a way that Riemann–Lebesgue theorem can be used to explain decoherence in a well defined final pointer basis. 相似文献
82.
Alain-Yves LeRoux Marie-Noëlle LeRoux Jean-André Marti 《Comptes Rendus Mathematique》2004,339(4):313-316
The source waves are some particular solutions to genuinely non linear hyperbolic systems with a source term, whose propagation velocity is a constant determined by the roots of this source term. We propose a system of 2 equations on a 2 dimension space, which model the velocity field of the atmosphere near the ground. The source term is made of three parts: a given pressure gradient, a friction or aspiration effect and the Coriolis force. In the case where these parameters are constant, we build a solution which is a constant outside a circular crown. The internal circle represents the eye's wall of the hurricane and corresponds to a share shock wave. The external circle is a set generating the bifurcation which actually models the hurricane. To cite this article: A.-Y. LeRoux et al., C. R. Acad. Sci. Paris, Ser. I 339 (2004). 相似文献
83.
Francisco Jesús Castro-Jiménez José Marı́a Ucha-Enrı́quez 《Comptes Rendus Mathematique》2004,338(6):461-466
We prove a duality theorem for some logarithmic -modules associated with a class of divisors. We also give some results for the locally quasi-homogeneous case. To cite this article: F.J. Castro-Jiménez, J.M. Ucha-Enr??quez, C. R. Acad. Sci. Paris, Ser. I 338 (2004). 相似文献
84.
In this paper an extension of the (r|X
p
)-medianoid on networks introduced by Hakimi (1983) is studied. In this extension the customer considers not only the distance
but some characteristics of the facilities such as store size, quality of service and parking space. A new firm wants to establishr new facilities which have to compete with thep facilities that already exist in the market. The entry firm wants to find their locations and characteristics to maximize
profits. Three different customer choice rules (binary, partially binary and proportional preferences) are considered. Some
discretization results are obtained and a resolution procedure is proposed. The problem is solved combining a global search
algorithm based on a branch and bound procedure with some combinatorial heuristics (greedy, interchange, and tabu search).
Some computational experiences are presented.
Partially supported by Ministerio de Ciencia y Tecnología (Spain) and FEDER, grant BFM2002-04525-C02-01. 相似文献
85.
86.
87.
88.
José M. Arrieta Neus Cónsul Anibal Rodríguez-Bernal 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2004,23(2):1-14
We prove the existence of nonconstant stable stationary
solutions of
an evolution problem with a nonlinear reaction acting on the
boundary. These solutions present layers at certain points of the
boundary. We also study the behavior of these solutions as the small
parameter appearing in the equation approaches zero and show some
stability properties of the profiles given by these equilibrium
solutions. 相似文献
89.
Summary The potential of liquid chromatography-mass spectrometry (LC-MS) has been studied for the simultaneous determination of sixteen carbamate and organophosphorus pesticides in honeybees using a traditional sample preparation protocol based on acetone extraction and dichloromethane partitioning. The performances of both atmospheric pressure chemical ionization (APCI) and electrospray (ES) interfaces were compared. APCI offered better sensitivity and specificity for a higher range of pesticides. Limits of quantification were from 0.01 to 0.17 mg kg–1, at which recoveries obtained were between 64 and 93%, except for pirimicarb that was at 13%, with relative standard deviations ranging from 7 to 20%. Fenitrothion, fenoxycarb, methiocarb and phoxim were found in bees from Valencian Community beehives at concentrations between 0.03 and 3.75 mg kg–1. 相似文献
90.
Isabel Brandariz José L. Barriada Teresa Vilari?o Manuel E. Sastre de Vicente 《Monatshefte für Chemie / Chemical Monthly》2004,343(6):1475-1488
Several reported procedures for calibrating glass electrodes in proton concentration are compared. Some recommendations for non-experts are also given. The examined procedures can be classified into two broad categories, namely: those based on direct potential difference measurements of solutions of known proton concentration and those that use one or several pH standards to calibrate the electrode and subsequently measure the pH of solutions containing known proton concentrations. With a single buffer, the two types of procedures lead to equivalent results. However, if two pH buffers are used, the slope of the calibration graph in proton concentration will differ from the real electrode slope to an extent proportional to the difference between the liquid junction potentials of the two buffers. Therefore, any other method is preferable under these circumstances. 相似文献